Portable refrigerated rig mat

ABSTRACT

A portable refrigeration mat includes an evaporator mat. An evaporator is located in the evaporator mat. Located above the evaporator mat is an insulation mat which thermally insulates the evaporator mat from the surrounding environment. Located above the insulation mat is a load mat having a planar load carrying upper surface. The evaporator is fluidly interconnected with a condenser to provide a thermosyphon unit which is portable and can be moved from site to site.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 61/336,006, the disclosure of which is hereby expressly incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to a portable and reusable equipment support mat, or rig mat, for use on frozen ground. When it is necessary to support equipment temporarily on areas where the ground is frozen for extended durations, such as in the arctic, an ice pad is built on top of the thermafrost substrate, portable rig mats are placed on the ice pad and the equipment is placed on the rig mats. However, the use of these mats is limited to the winter and spring when the thermafrost substrate remains frozen. As a result, work cannot continue in these regions when the thermafrost substrate begins to thaw. Since the use of these mats for activities such as drilling for oil does not have a predefined time limit, it may be necessary to remove all of the equipment if the activity has to extend beyond when the ground will support the mat and then restart it the next winter.

This problem is overcome when a permanent structure is constructed in this environment by placing the structure on top of a thermosyphon which prevents the ground that is supporting the structure from ever melting. A passive thermosyphon works when the outside air is colder than the ground. In a passive thermosyphon, an evaporator is buried in the ground below the structure. The evaporator is fluidly connected to an above ground condenser. As the ground warms, it warms the refrigerant in the evaporator to where it becomes a vapor. The warmed vapor then rises to the condenser through interconnected pipes where the cooler outside air then cools it. When the vapor is cooled, it condenses and drops back into the below ground evaporator. This cycle is then repeated. As the refrigerant is warmed in the evaporator, it draws heat out of the ground and keeps the ground from melting. When the outside air is not colder than the ground, the condenser can be replaced with a heat pump or another type of refrigeration system. While thermosyphons work well in supporting a structure permanently on frozen ground, they cannot be moved and thus are not cost effective in situations, such as drilling for oil, where the equipment is going to be used for a temporary period.

BRIEF SUMMARY OF THE INVENTION

A portable refrigeration mat includes an evaporator mat which can be thermally insulated from the surrounding atmosphere. The evaporator mat includes an evaporator cavity which is enclosed by a cover. An evaporator is located within the evaporator cavity. The evaporator mat is fluidly interconnected with a condenser to provide a thermosyphon unit which is portable and can be moved from site to site.

The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is an exploded perspective view, looking from above, of a portable refrigerated rig mat embodying the subject invention.

FIG. 2 is a plan view, partially broken away, of an evaporator mat which is an element of the invention.

FIG. 3 is an exploded perspective view, looking from above, of an insulation mat which is an element of the invention.

FIG. 4 is a cross-sectional view of the insulation mat of FIG. 3.

FIG. 5 is a perspective view, looking from above, of a load mat which is an element of the invention.

FIG. 6 is an exploded perspective view of the load mat of FIG. 5.

FIG. 7 is an exploded perspective view, looking from above, of an alternate version of the load mat.

FIG. 8 is a schematic view of the rig mat of FIG. 1 with a passive thermosyphon system.

FIG. 9 is a schematic view of the segment of FIG. 1 with an active refrigeration system.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring now to FIG. 1 of the drawings, a portable refrigerated rig mat 10 includes three distinct elements which can be transported separately and assembled as a unit onsite and then moved to another site and reused if desired. Because each element is separate, the elements do not have to be utilized together. Referring now also to FIG. 2, the bottommost element is an evaporator mat 11. The evaporator mat carries and protects an evaporator 12. The evaporator mat must support the weight of the other two elements and the equipment which will be placed on the mat. The evaporator mat can comprise a rectangular steel evaporator frame 14 which defines an evaporator cavity 15. The frame can be constructed from standard structural steel I beams or channels which are joined to one another by welding or similar methods. Side beams 16 are located on each side of the frame. End beams 17 extend between the ends of the side beams. Cross beams 18 can extend between the opposed sides of the frame and longitudinal beams 19 can run between opposed ends of the frame to provide additional support.

In the embodiment illustrated, supported in the frame are a series of evaporator pipes 20 which have ball valves 22 with pressure release vents attached to each end. The frame 14 is covered top and bottom with a cover 24 which can be steel plates or plates of steel mesh 24. Openings 26 are located in the covers 24 above the valves 22. The size of the evaporator mats 10 and the number and diameter of the evaporator pipes 20 vary depending on the particular use of the mat. The evaporation mat is set on top of the ice pad. The outer periphery of the evaporator mat may be covered by a rubber seal (not shown).

Located in the ground above the evaporator mat 11 is an insulation mat 30 which thermally insulates the evaporator mat from the environment outside of the portable refrigerator rig mat 10, FIGS. 3 and 4. The insulation mat has the same footprint as the evaporator mat. The frame 32 of the insulation mat can be made from a fiber reinforced plastic material. The frame side beams 34 may be I shaped in cross-section. The side beams may be interconnected by end beams and cross beams 36. The end beams and side beams 36 are slightly shorter than the side beams so that they nest in the side beams. The beams 34, 36 are joined by mechanical means, such as bolts or rivets, or by gluing them to one another. Fiber reinforced plastic spacers 38 are installed on top of the flanges on each side of the cross beams. The spacers have a thickness approximately equal to the thickness of the top and bottom flanges of the side beams 34 to bring the tops of the spacers flush with the tops of the side beams. The top and bottom of the insulation mat 30 are covered by an ultra-high-molecular weight polyethylene skins 40. The skins 40 are attached to the frame 32 by mechanical fasteners or an adhesive in a manner that makes the frame watertight and impervious to water vapor. Openings 42 are placed in the skins 40 aligned with the openings 26 in the evaporator mats 11. Access doors (not shown) cover the openings 42. The access doors are watertight and impervious to water. The outer vertical periphery of the thermal mat may be covered by a rubber seal 46 to form a water barrier. The open cavity at the center of the thermal mat is filled with blocks of Styrofoam insulation 48. It has been found that DOW CHEMICAL Sharp Edges Polystyrene works well for this purpose. In the embodiment illustrated, the two center insulation blocks have a combined thickness equal to the height of the side beams 34. Located on each side of the center blocks are thin sheets of insulation having a thickness equal to the spacers 38.

Referring now to FIGS. 5 and 6, the topmost element is a load mat 50. The load mat has the same footprint as the evaporator mat and the insulation mat. The load mat has a steel I beam or channel frame 52 similar to the frame 14 of the evaporator mat 11. Located between the frame elements is a floor 54 made from groups of engineered glue lam beams 56. It has been found that certified glue lam beams made from Douglas fir work well for this purpose. Framed openings 58 are placed in the beams 56 above the openings in the evaporator mat and the insulation mat to provide access to the valves. The openings are covered by doors 57. The outer periphery of the load mat may be covered by a rubber seal 46.

The best method of installing the glue lam beams is to lay one side frame in a jig along with the cross members, weld them together, and then stand them on their side. The glue lam beams are then inserted on edge between the beam flanges by rows, letting gravity hold them in place. As the glue lams are inserted, longitudinal beams are installed to keep the glue lams in place. In this way, each layer of glue lam beams is boxed in as it is built. Fork tubes 58 are provided in the sides of the protective mat to allow the protective mat to be lifted by a forklift.

In use the portable refrigerated rig mat is assembled on top of an ice pad 70. When the conditions are right, the evaporator 20 will be fluidly connected to a condenser 62 by pipes 64 to create a passive thermosyphon, FIG. 8. When the air is not sufficiently colder than the ground, the evaporator 20 will be connected to a heat pump 66 through pipes 68 to create an active cooling system, FIG. 9. In either event, the evaporator pad is isolated from the outside environment. Its bottom is exposed only to the ice pad and its top is insulated by the insulation pad 30. Its edges are insulated by a rubber seal 46. Because the portable refrigerated rig mats are installed in side by side rows and columns over a large area, most of them are completely thermally isolated from the surrounding environment and the evaporator will not be effected by the outside air temperature. Because the ice pad can be quite extensive and many portable refrigerated rig mats will be placed on it, the evaporators of adjacent mats may be connected to one another and the condenser or heat pump will service all of the interconnected evaporators.

The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow. 

1. A portable refrigeration mat comprising: (a) an evaporator mat; (b) said evaporator mat including an evaporator frame which defines an evaporator cavity which is enclosed by a cover; and (c) an evaporator located within said frame.
 2. The mat of claim 1 wherein said evaporator mat is capable of supporting a load.
 3. The mat of claim 1 further comprising: (a) an insulation mat located on top of said evaporator mat; (b) said insulation mat including an insulation frame defining an internal insulation cavity; (c) a skin attached to said installation frame in a manner to seal said insulation cavity watertight; and (d) insulation material which at least partially fills said insulation cavity.
 4. The mat of claim 3 wherein said insulation mat is capable of carrying a load.
 5. The mat of claim 3 further comprising: (a) a load mat capable of carrying a load; (b) said load mat located on top of said thermal mat; wherein (c) said load mat has an exposed upper surface which is generally planar.
 6. The mat of claim 1 wherein said evaporator frame is metal.
 7. The mat of claim 1 wherein said cover is a solid metal sheet.
 8. The mat of claim 1 wherein said cover is an expanded metal sheet.
 9. The mat of claim 1 wherein said evaporator is a series of hollow pipes.
 10. The mat of claim 3 wherein said insulation frame is fiber reinforced plastic.
 11. The mat of claim 10 wherein said skin is ultra-high molecular weight polyethylene.
 12. The mat of claim 1 wherein said load mat comprises: (a) a frame; (b) a plurality of side-by-side glue lam beams; wherein (c) said frame carries and holds said beams in side-by-side contact as an integral unit.
 13. The mat of claim 1 wherein said evaporator is one or more hollow pipes.
 14. The mat of claim 1 further comprising an above ground condenser which is fluidly connected with said evaporator to create a thermosyphon.
 15. The mat of claim 5 wherein said load mat, insulation mat, and evaporator mat have the same footprint.
 16. The mat of claim 5 wherein each of said load mat, insulation mat, and evaporator mat is portable and is an integral unit which can be moved and reused at a different location.
 17. A portable refrigeration mat comprising: (a) an evaporator mat containing an evaporator; (b) an insulation mat located on top of said evaporator mat; (c) a load mat having a planar load supporting upper surface, said load mat located on top of said insulation mat; and (d) wherein said insulation mat provides a thermal barrier between said evaporation mat and said load mat.
 18. The mat of claim 17 including a condenser which is fluidly connected to said evaporator mat to form a passive thermosyphon.
 19. The mat of claim 17 including a refrigeration unit which is connected to said evaporator to form an active thermosyphon.
 20. The mat of claim 17 wherein each of said load mat, insulation mat, and evaporator mat is portable and is an integral unit which can be moved and reused at a different location. 